Radio apparatus



Aug. 25. 1931. v. J. FABlAN 1,820,059

RADIO APPARATUS Filed Feb. 19, 1926 2 Sheets-Sheet 2 &@

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gmmtw Whmr Famn Patented Aug. 25, 1931 UNITED STATES l,82ll,059

PATENT caries RADIO APPARATUS Application filed. February 19, 1926. Serial No. 89,471;

This invention relates to radio apparatus and, more particularly, to audio frequency amplifier systems including methods and apparatus used in connection therewith.

A primary object of the invention is the provision of an audio amplifier system wherein greater uniformity of load distribu tion in the first stage audions is obtained,

my without signal-distortion, and with increased signal intensity when filament energization is either from an alternating supply source or from a storage battery.

A further object of the invention is to provide an audio frequency amplifier or amplifier system in which audions having metal filaments draw energy from a source of alternating current, such as that ordinarily supplied to dwelling houses for lighting purposes, stepped down to the desired potential through a suitable transforming device.

A further object of the invention is the provision of a system of this character, dc-

2;; signed to output without distortion signals which otherwise would become distorted in the amplifier due to the alternating or other current supply being introduced into the circuit, which system has incorporated with- -3 in itself, as an integral part of the circuit, a method of inducing signals over neutral grids in such way that no external device for rectification is necessary.

A still further object of the invention is the provision of a system of this character which is capable, without any changes in the circuit of the amplifier, of satisfactory operation from either alternating or direct current sources when metal filaments are used.

A still further object of the invention is the provision of a system of this character which may be manufactured and maintained at a comparatively low cost. which is simple and easy of operation, and which will deliver a signal of superior quality and of sufiicient volume for operating successfully and (ll iC GZltlY available loudspeakers.

lVith these and other objects in View,

LY-J which will become apparent as the description proceeds, the invention consists of the novel features of construction, combinations of elements and arrangements of parts hereinafter to be fully described and pointed out in the claims.

A full and complete understanding of the invention may be obtained from a consideration of the followingdetailed description, taken in connection with the accompanying drawings forming a part of the disclosure, it being understood that while the drawings show certain practical embodiments of the invention which have proven satisfactory in use, the latter is not to be confined to the showing thereof but may be changed or modified so long as such changes and modifications mark no material departure from the salient features of theinvention as hereinafter described and claimed.

In these drawings:

Flgure 1 1s a dlagrammaticview of a sys tem embodying the features of this invention in which two audions are employed and have their filaments energized by an alternating current source; 5

Fig. 2 is a similar View illustrating the system whenthree audions are employed, or four audions may be employed by carrying out the circuit'in Fig. 3 progressively;

Fig. 3 is a diagrammatic view of a modified form of circuit, showing clearly the capacity free grids or isolated grids, and circuit;

Figs. 4, 5 and 6 are diagrammatic views illustrating other modified forms of circuits; and

Fig. 7 is a diagrammatic conventional view illustrating the connections for utilizing the amplifier shown in Fig. 1 for amplifying the sound-producing currents transmitted by a telephone transmitter.

Referring to the preferred embodiment of the invention as illustrated in Fig. 1, the filaments 1 and 2 of the respective vacuum tube amplifiers 8 and 4 are supplied with current from the secondary winding 5 of an ordinary, bell'ringing transformer 6 of such a ratio that when its primary 7 is connected to a source of alternating current, such as is usually provided in dwellings for lighting purposes, a potential of approximately eight volts will be impressed upon the filaments, optionally or from a suitable battery source, a variable resistance 8 being included in circuit to permit regulation of this potential. While I have specified the voltage as eight, it is to be'understood that it may range from one to twelve and, in any event, be suificient to take care of any drop due to existing conditions.

As shown, a wire 9 having connection with the negative pole 10 of the B battery 11, common to a detector circuit (not shown) and an amplifier circuit, is connected at one end to either the positive or negative de tector filament of the detector circuit, and at its other end is connected to wire 12 leading from terminal 13 of transformer secondary 5 directly to the so-called negative terminals 14 and 15 of the respective filaments 1 and 2. Wire 16 connects the terminal 17 of the winding 5 through the variable resistance 8 to the positive terminals 18 and 19 of the respective filaments 1 and 2. The positive terminal 20 of the B battery 11 connects through a resistance 21 of approximately 100,000 ohms to the plate terminal 22 of tube 3 and also through a variable resistance 23 of 25,000 to 50,000 ohms to one terminal 24 of a jack 25 designed to be connected to any available form of loud-speaker (not shown). A second terminal 26 of the jack connects directly to the plate terminal 27 of tube 4. A fixed condenser 30, preferably of from .0025 to .006

microfarad capacity, is connect-ed between,

plate terminal 22 of tube 3 and grid terminal 29 of tube 4. 7

An audio transformer 31, in this instance, is employed to conductively input thesignal or the signal-producing currents from the detector circuit into the amplifier.

of the transformer 31 are to be connected to the positive B battery terminal and to the plate terminal, respectively, of the detector system (not shown). Terminal 35 of the secondary winding 36 of the transformer 31 connects directly to the grid 37 of tube 3, and the terminal 38 of the winding 36, instead of connecting to the filament terminals 14 and 15 which would result in the usual filament return of the tubes 3 and 4. is connected directly to grid terminal 29 of tube 4 by wire 39, and forms the isolated capacity free grid circuit. Condensers 40 and 41, preferably fixed and of approximately .001 to .002 microfarads capacity, may be connected between terminals 35 and 38 and between jack terminals 24 and 2 respectively, if desired;

The modified circuit shown in 2 includes all of the elements shown in Fig. 1 and above described and, in addition, illustrates the manner in which other stages of The terminals 32 and 33 of the primary winding amplification may be added and connections whereby optional use of a storage battery or an alternating source of filament energy may be obtained.

As shown, an audion 42 is resistancecoupled to the audion 4 through resistances 43, preferably of one-half megohm resistance, interposed between grid 44 and negative filament lead 12 and resistance 45, preferably of 100,000 ohms resistance, interposed between plate 27 of audion 4 and the positive terminal 20 of the battery 11, the plate and grid terminals of these resistances be ing shunted by a fixed condenser 46 of approximately .006 microfarad capacity. The terminal 26 of the loud-speaker jack 25 is connected directly to plate 47 of audion 42 instead of to plate 27 of audion 4, and the resistance 23 is inserted in circuit at jack terminal 24 in the positive battery lead 48, or four stages may be obtained by using twoof the circuits illustrated in Fig. 3.

The means for selectively feeding the audion filaments with alternating current or from a direct current source, as shown, include a conventional double-throw reversing switch 49, the lower terminals 50 and 51 of which connect, respectively, to the positiveand negative terminals 52 and 53 of a storage battery 54. The upper terminals 55 and '56 of the switch 49 connect, respectively, to the terminals 13 and 17 of the secondary winding 5, and the center terminals 57 and 58 of the switch connect, respectively, to filament feed lines 12 and 16. Preferably and as shown, a fixed condenser 59 of approximately .0001 micro-- farad capacity is bridged across the grid 44 and plate 47 of audion 42 to modulate any harsh effects produced in this tube.

In Fig. 3 ofthe drawings is illustrated the simplestoperative form of amplifier in accordance with this invention. This figure illustrates specifically theisolated capacity grid circuit. This circuit is identical with that disclosed in Fig. 1, with the exception that the condenser 40 and resistance 28 are omitted, and it has proven operative and fully satisfactory for certain purposes.

The embodiment of the invention illustrated in Fig. 4 is similar to that shown in Fig. 1,,with the exception that a split secondary audio transformer 60 replaces audio transformer 31. As shown the two outer secondary terminals 61 and 62 are connected, respectivelyato grid 37 of audion 3 and in grid 29 of audion 4,'the center secondary tap 63 being connected to terminal 64 of resistor 28. A' small capacity condenser 65 is, in this instance, inserted between the terminals 64 and 29.

The embodiment of the invention illustrated in Fig. 5 illustrates the use of an audio transformer 66 in lieu of resistors'21 Ila and 28 and condenser 30 as employed in the embodiment shown in Fig. 1.

Fig. 6 illustrates the employment of an air core transformer 67 in lieu of or with the resistors 21 and 28 and condenser 30; this being particularly useful at radio frequencies: My inventive-concept is applicable to detector systems at radio frequencies in which it functions in substantially the same way and utilizes the principles as herein set forth. I shall forthwith file an application for patent to protect the same as applied to this other system.

Fig. 7 illustrates the application of the present invention as an acoustic amplifier in connection with a transmitting source, here shown as a microphone 68.

Putting the amplifier into operation, as illustrated in Fig. 2 (for instance) and assuming that it'is operating on alternating current, with signals being actually output, the removal of audion 3 from its position does not stop signal flow to audion 4 which is receiving the impulse direct from audio transformer 31 through lead 39, but amplification has perceptibly decreased and distortion by reason of alternating currents becomes apparent, which fact conclusively indicates that audion 4 is receiving the original signal as described simultaneously with audion 3 but which it cannot completely rectify in itself. The replacing of audion 3 in its proper position immediately clears up this distorted condition and the aforementioned superior amplification is resumed. This is readily borne out by plugging the loudspeaker in on audion 4 or 42 during this test. New, plugging the loudspeaker in on audion fl and removing audion 4 from its illustrated position, the output of audion 3 will become distorted though not as much so as was noticeable when audion 3 was removedand amplification is reduced. Signals continue to be impulsed, however, through lead 39 and transformer 31. Plugging in on audion shows it distorted and receiving no signals; plugging back on audion 3, replacing audion 4, distortion ceases and greater amplification results, which indicates conclusively that there is an interaction between audions 3 and 4 and that signals are being input therebetween and that complete rectification, amplification and load distribution can be accomplished only when the circuit is intact. When plugged in on audion 42, we

. find. that the resulting combined amplified signal of the two audions 3 amplified with tremendous distortion, suitable for all practical purposes for which the amplifier is intended. It appears that audion 42, by reason of its association with audions 3 and 4 and the infiu ence of the action of these on 42, participates in the rectifying action described with respect/to the interaction between audions-'3 and 4 is being volume and no and 4, resulting from the capacity circuit employed. The signals resulting from this system are being output with all the superior and desirable qualities which result from the interaction of audions 3 and 4 alone, despite the fact that audion 42 receives the alternating on rent aswell as audions 3 and 4. As nearly as I can determine, the action of the latter impart their rectifying influence on audion 42 also, inasmuch as the latter receives from audions 3 and 4 a very highly amplified signal which it outputs and which is not distorted to any appreciable extent in audion 42. In other words, whatever impurities may exist in eliminated by the volume and amplitude of the signal imparted to it from audions 3 and 4. Continuing the test under consideration and still plugged in on audion 42, but removin audion 4,

indicates that audion 42 now receives no portion of the original impulse signals. Replacing audion 4 and removing audion 3, distorted signals again audion 42, which bears out previous tests that audion 4 receives the signal simultaneously with audion 3.

The action of this amplifying circuit does not stop here, however, in its It not only rectifies alternating current impurities, but there is a more evenly distrib uted volume load in the first stage audions and this increased load is impressed upon audion 42. With this tremendous volume, the amplifier requires no C battery grid bias and none is desired, as the output is perfect for all practical purposes and is superior tothe output of standard amplifiers in volume, quality and frequency range. This volume is evidently practically the full volume of the capacity of the tubes. Power audions may be used in any or all stages interchangeably with other types of tubes, or power tubes may be employed in all. stages with out a C battery and with excessively high B battery potentials without distortion and without intercapacity effects. It has been observed that when the amplifier, as shown in Fig. 2, for instance, has a short time, the audions heat up considerably, and it has also been observed that the audion 42 becomes warmer than audion .4, and audion 4 becomes warmer than audion 3 which remains comparatively cool.

Analyzing further, I find that the output of this amplifier has a basicly more solid and intensified signal strength, truer in reprduction without distortion of the original transmitted signals. I believe this to be due to the process described as occurring in audions 3 and 4 which not only rectify, and amplify but give more solid base and'intensity to the impulse signals, resulting from the wide frequency range and high ampliaudion 42, if any, are 180 signals cease and increased alternating hum or distortion sets in, which are output through;

superiority. 1

been in operation for l tude of signal which results in well-modulated, full-rounded tone qualities of music, voice and code. This will be especially noted in instrumental music, such as piano and violin, and soprano renditions.

The action of the audions resulting. from the arrangements and connections of the instrumentalities as herein disclosed, in using alternating current as heating energy, are explained as follows:

As the capacity grid circuit l tive potential iss no negait is in a capacitatively isolated circuit. lVhen the positive sine of the alternating current effects any of the free grids in the circuits in such a way as to tend to make them positive, electronic flow is instantly set up from filaments to such grid positive stray current, and as the stray positive current is trapped in the isolated capacity grid circuit leading from the grid to a zero point in the secondary winding of the transformer 31, it cannot go farther than such zero point and is instantly made negative by the electronic filament-to-grid flow. Thus, the free grids during and in between such cycle of perforn ance remain at the complete zero or at a slight negative potential due to the proximity to the filaments, while the secondary 31 must remain at ero potential at all times between the free unenergized grids. The greater the electronic flow, the more negative the free grids become in closer resonance with. the filaments, and when the circuit is possessed of a signal it further causes a still greater electronic flow and makes the isolated grids still more negative. In such a cycle of action, self-rectifying, self-compensating characteristics of this method also become self-biasing to satisfy all requirements for the peak performance of tubes and transformers for both tone amplitude, frequency range, and truthful reproduction of signals input, as will be hereinafter explained. There is a distortion common to resistance-coupled amplifiers, which is due to changing of the impedance of the coupling condensers, which becomes a serious consideration only when load is applied to that circuit. Such a circuit carries such a load divided into two portions, that of the grid circuit itself and that of the grid resistance, or grid leak, the use of which is necessary in such types of amplifiers. In accordance with my inventive-concept, due to the structural means and the isolated capacitative methods employed, no such resistance leak is used and no direct energy source representing load is employed; thus, this distortion source is eliminated. Fun ther, as the transformer secondary Bl is connected direct to the free isolated grids at all terminals with no current load, no current can or does flow in this winding, nor is such current desirable for'inputing signals, thus eliminating any distortions therein.

lation; thus, battery purpose of adaptability to either alternating? Should any stray'currents be entrapped in this winding and the circuit, they are eliminated in the rectifying action of the tubes instantly, as previously explained. Thus, there is zero or neutralized potential in this winding at all times, which not only. eliminates any distortion but permits the use of much higher ratios and the frequency range is broadened to its maximum limitations. Standard tubes are adjudged to produce maximum all-around efiiciency, when the gridsare only at a slight negative potential in respect to filament potentials. In practical systems now used, this is accomplished by. the use of a grid bias energy (or a O battery) or a resistance. In accordance withmy inventive-concept, this is automatically taken care of by the performance of the capacity circuit isolated grids, as hereinbefore explained. In consideration of. all these facts pointed out above, it will be seen that the free grids cannot become positive or remain so under any conditions and, in addition, must remain at a very slight negative potential and the isolated part of the 1: circuit itself contains no potential at all. While the grids may receive, or be purposely given, a slight positive char e during acycle of performance, this is instantly made negative and remains so, remaining at maximum saturation butin relation and phase to and with the negative filament energy and potentials. This is the theoretical ideal so much sought for in amplifier systems, and

this ideal condition is brought about or made possible by the employment of the isolated capacity grid circuit herein described.

Battery noises are noises created in the chemical action of batteries and throw oil noises of parasitic electronic flow in tubes caused by this action. In the above describedsystem, not only most of the noise but practically every particle of battery grind is absorbed in the filament circuit of the system, or in the plate circuit, and does not manifest itself noticeably in the signal output, for the same reason that alternating current distortions are rectified through isogrind is eliminated for and battery noises, for 5.115

ire

all practical purposes the most part, also.

If the signal be of large tonal amplitude, the mean grid potential is in direct proportion made so negative at the'grids asto keep the maximum positive potential at zero {31,5 peak in respect to filaments, thus causing the amplifier action to adjust itself to an ideal condition for any and all signals, of all amplitudes and frequencies, and perfect ly reproduces and amplifies the same with 312 no loss of volume, there being no precedent for the simple. accomplishment of these results.

This circuit has been constructed with the tem to a detector batter or other suitable direct current filament supply sources. The herein-described amplifier not only practically overcomes the alternating ripple, chatter or hum when an alternating source is employed, but also damps out the tube ply sources are used.

It has been found in actual practice that after using audions in this amplifier on alternating current for a period of several months, instead of becoming insensitive for use at radio frequencies or as detectors, they have seemingly lost none of their sensitiveness but have apparently actually gained therein and may be used alternately at radio or audio frequencies.

The output is so undistorted that the adjustment of available types of loud-speakers is possible up to the rattling point of the diaphragm with a clear signal output.

The amplifier will operate satisfactorily at plate potentials as low as fifteen volts and up to potentials so high that the tubes become inoperative, that is, well over two hundred volts on three stages.

Due to the lack of internal capacity effects, a compact arrangement of the apparatus is possible, which permits the building of the amplifier as an integral part of a receiver set or as a separate unit.

Summarizing, the herein-described amplifier will utilize any available form of amplifying type audions, without either A or C batteries. It requires so little adjustment, is so stable, simple and positive in operation as to be of inestimable value for general pur poses; Using it with a one-tube detector, with such a wide range of B battery plate potentials, the receiver embodying the amplifier would operate as cheaply for all practical purposes as would the one-tube detector in itself, and with all the superior qualities related above. With detectors employing two or more radio frequency tubes of drycell type, the operation costs would be negligible. The capability of this amplifier to operate efliciently on practically any available source of supply renders it of universal application.

lVhere I have herein used the term signal and equivalent terms, I intend to refer thereby not only to a radiant energy delivered to an antenna system by a transmit ting system, impulsed by the antenna syssystem for output to an to a desired audibility, waves as the same may be impulsed upon the amplifier system through a source of transmission such as a telephone or microphone, or a diaphragm adapted to set energy into motion.

In employing the term transformer herein, I intend it and equivalent terms to comprehend any device or capacity appropriate for amplified systems and adapted to amplifying system but, also, to sound noises when direct sup-- may be of the usual character,

take a primary potential of one value and induce a secondary potential suitable to transfer supply or signal energies of predetermined value for introduction into the circuit.

I have herein used the term direct current as con'iprehending any unidirectional current as, for instance, a battery or a machine-generated current. Where a machinegenerated current is employed, I would, of course, employ an appropriate resistance between the source and amplifier to deliver the proper potential to the system.

Where I use herein the term free grids I mean to convey that the grids of the thermionic valves are freed of a negative high potential current, are isolated capacitatively, and to all intents and purposes are possessed of nonegative current potential as in common practice.

My inventive-concept involves not only apparatus but, also, a method with which such apparatus is utilized.

It is to be understood that'the apparatus although my concept also contemplates utilization of any types of devices or capacities which may be found to promote efiiciency.

My invention is to be distinguished from What has heretofore been proposed, in that it functions in the manner herein explained without the employment of any means or instrumentality external of the amplifier system for rectifying the current supplied thereto. My concept involves means for rectifying, within the amplifying system it self, in other words, the'audions in conjunction with the circuit and method employed, themselves function not only to amplify but also to rectify and, thus,,are the only means usedin the system for effecting rectification.

I am aware of the fact that audions have heretofore been utilized to function as rectifiers of radio impulses or audio frequencies on the onehand, and, on the other hand and separately, as rectifiers of current energies as in filter systems; but, so far as I am'aware, a plurality of audions have not heretofore been used in such manner that an interaction between them affects rectification of current energies concurrently With and duringtheir individual action as amplifiers of signals. In other words, I believe that I am the first to aggroup two or more audions and a suitable circuit in such manner that each will function individually as an amplifier and concurrently therewith and in coaction with a companion audion by interaction of a capacity circuit and free grids, effect rectificationand with resultant greater signal volume and quality than has heretofore been derived from audions operating merely as amplifiers. This advance in the art resides primarily in simultaneously impulsing signals to the grids of two companion audions putting the resulting signal.

and the capacitative free grid circuit without current thereon, whereupon byinteraction of the audions they function in the unique manner hereinabove set forth.

What I claim is: Y 1. The herein-described method of amplitying signal energies introduced into an amplifier including a plurality of audions, which includes the steps of simultaneously impulsing a signal upon the audions, amplifying this signal in one of the audions, then combining the original signal present in the second audion with the amplified signal, amplifying the combined signal, and out- 2. In an audion-coupled circuit a source of signal current, an audion having a plurality of cold electrodes and a hot cathode, means insulated from the hot cathode and nonconductive to direct currents forming a path from said source of signal current to one of said cold electrodes, and means nonconductive to direct currents connecting the second cold electrode to the first cold electrode through said first-mentioned means.

3. In an audion-coupled circuit a source of signal current, an audion having a plurality of cold electrodes and a hot cathode, means insulated from the hot cathode and :conductive only to signal currents forming a path fromsaid source of signal current to one of said cold electrodes, a source of potential connected between the other cold electrode and said cathode, and means in said connecting circuit for causing a potential drop externally between said cathode and electrode of a magnitude substantially equal to the potential drop therebetween within the audion.

4. An audion-coupled circuit including a source of signal current, audions each having a filament, plate, and grid, means insulated from the filaments of the audions connecting the grids of associated audions with the source of signal current and means connecting the plate of one of said audions to the grid-connecting means, both of said means being such as to pass signal currents but non-conductive to the passage of unidirectional currents.

5. An audion-coupled circuit including a source of signal current, a plurality of audions each having a filament plate and grid, an input circuit completely insulatedfrom the filaments of the audions connecting the grids to the source of signal current, and means connecting the plate of one of said audions to the grid of an associated audion, said means being such as to allow passage of signal currents but completely blocking direct currents.

6. An audion-coupled circuit including a source of signal, current, a plurality of andions each having a filament plate and grid, an input circuit completely insulated from the filaments of the audions connecting the grids to the source of signal current, means connecting the plate of one of said audions to the grid of an associated audion, said means being such as to allow passage of signal currents but completely blocking direct currents, and means between the plates of the audions and a source of potential adapted to maintain a potential drop between said source and said plates such as to bring the constants of the audions and the potential on the plates to a mean operative characteristic.

In testimony whereof I affix my signature.

VINCENT J. FABIAN. 

